Is it Normal for Espresso to Have Sediment? What Causes Coffee Residue in the Cup?

Understanding Sediment in Espresso Shots

A friend recently asked FrontStreet Coffee, "I've been noticing some black particles settling at the bottom of my espresso shots lately. Is this normal?"

While this might seem unusual, it's actually a normal phenomenon! These black particles settling at the bottom of espresso are actually coffee grounds that have passed through the mesh screen of the portafilter. Generally, having a small amount of coffee particles in one shot is normal.

Why Does This Happen?

As we know, filter paper currently offers the best filtration quality, capable of blocking solid particles and oils, resulting in coffee with the highest clarity. However, the portafilter basket used for espresso extraction consists of tiny holes that act as a filtration system. If you hold a portafilter basket up to light, you can see light passing through these mesh openings.

During pressurized extraction, some fine particles inevitably pass through these tiny holes and fall into the coffee liquid.

Fine Particles in the Crema

You may have heard of "tiger strip crema" - those black stripes floating on the golden crema, resembling tiger stripes. These black stripes are actually extremely fine coffee particles that have passed through the portafilter mesh into the cup. If you let it sit for a while until the surface crema dissipates, these fine particles will settle to the bottom of the cup.

The appearance of "tiger strip crema" doesn't necessarily indicate a poorly extracted shot, nor does it mean it's exceptionally good. It simply has a distinctly different appearance from typical crema, but in terms of quality assessment, "tiger stripe crema" is still considered normal.

Why Am I Suddenly Noticing Sediment in My Espresso?

Continuing to answer our friend's question, from their wording, it seems this didn't happen before and has only recently appeared, making it seem unusual. FrontStreet Coffee has summarized several possible reasons:

It's Always Been There - You Just Didn't Notice

Fine particles that fall into the coffee cup don't immediately sink to the bottom. They take about 4-5 minutes to settle. When drinking espresso directly in one go, most of these fine particles are consumed along with the coffee liquid, leaving the cup appearing clean. Of course, this small amount of fine particles won't affect the taste or pose any health risks.

However, with drinks like Americano coffee, which have larger volumes and take several minutes to finish, and are consumed in smaller sips, the fine particles are more likely to settle at the bottom. As you near the end of your drink, these particles at the bottom become visible.

Coffee Ground Too Fine

If you notice an unusually large amount of sediment in your coffee, it might be due to incorrect grinding parameters (too fine). When adjusting espresso grind settings, we typically follow the formula of ratio and time. That is, if the extraction ratio is correct and the time is correct, then this grind setting is appropriate.

FrontStreet Coffee offers an example model: suppose we all use a 1:2 coffee-to-liquid ratio with 30 seconds as the standard for determining grind size.

When the grind setting is at 2.0, 20g of coffee yields 20g of liquid in 30 seconds;

When the grind setting is at 1.7, 18g of coffee yields 36g of liquid in 30 seconds.

This means that with less coffee, to maintain the same extraction time, the coffee needs to be ground finer. And when coffee is ground finer, there's a higher probability of coffee particles passing through the mesh holes and settling at the bottom of the cup.

Deformed Portafilter Mesh

Long-term exposure to high temperatures and pressure can cause the mesh holes in a portafilter to enlarge. This phenomenon isn't common and typically only occurs after 1-2 years of intensive use. The check is simple - hold the portafilter up to light and observe if any of the tiny holes have become enlarged.

Important Notice :

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